In a nuclear reactor, a core of nuclear material is confined to a small volume internal to the reactor so that a reaction may occur. In many instances, a controlled nuclear reaction may persist for an extended period of time, such as several years, before refueling of the reactor core is required. Accordingly, when used as a source of heat for converting water into steam, a properly designed nuclear reactor may provide a carbon-free, stable, and highly reliable source of energy.
A nuclear reactor may make use of a working fluid, such as water, which may be converted to steam at a pressure significantly above atmospheric pressure. The pressurized steam may then be used to drive a turbine for converting mechanical energy to electric current. The steam may then be condensed back into water, and returned to the reactor. In many nuclear reactors, the cycle of vaporization, condensation, and vaporization of the working fluid may continue day after day and year after year. One feature of a nuclear reactor may be a steam generator that receives liquid coolant (e.g., flushed through the inner diameter (ID) of a matrix of several closely spaced thin-walled metal tubes) at an input side, vaporizes the coolant by way of exposure from the heat source of the nuclear reactor to the outer diameter (OD) of the steam generator tubes, and provides the vaporized coolant to the input of a turbine.
Steam generator tubes may sometimes need to be inspected for flaws that may compromise structural integrity of such tubes, potentially allowing the radioactive heat fluid on the OD to mix with the vaporized liquid on the ID which flows to a turbine. Such inspections are performed by inserting eddy current probes, containing a probe head with an electromagnet coil mounted on a probe shaft, through the tube bore. Such probe shafts, however, have limited flexibility and are difficult to pass through the bore of the tubes, for example when those tubes have multiple or compound tight radius bends or in regions where the tubes bend.